connection serial port to CPLD

[yasin]

Hi,
I know that 8051(microcontroller) has an UART (Universal Asynchronous Receiver/Transmitter) itself, but CPLDs have not it.
Now, should I use from an UART chip for connection serial port to CPLD? (Yes or no)
If yes, what is type of chip? and should it use ago or after MAX232?
If no, is interfacing IC between serial port & CPLD just a MAX232?
Please introduce to me a template about connection serial port to FPGA/CPLD.
Thanks a lot

 

[alt007]

hi ,
u need to have max232 on ur board attached to UART implemented in ur CPLD.
Regards
Lalit

 

[bmwcoupe]

hi

you need to have MAX232 or similar to convert logic levels
from RS232 to LVTTL/LVCMOS .............
but you also need to write UART TX, UART RX codes in vhdl
to implement your UART in the cpld........


good luck.
bmwman.

Added after 32 seconds:

hi

you need to have MAX232 or similar to convert logic levels
from RS232 to LVTTL/LVCMOS .............
but you also need to write UART TX, UART RX codes in vhdl
to implement your UART in the cpld........


good luck.
bmwman.

 

[Iouri]

You DONT NEED to have Max232 chip to connect 8051 to CPLD. Few thinks I think you need to consider:
1. Make sure CPLD and 8051 are both 3.3V or 5V devices.
2. Check Xilinx website for the appnotes related serial port implimentations

Good lack

 

[victors]

Just to add on. The MAX232 will generate voltages of -10V to +10V and will destroy either the 8051 or the CPLD. The +-10V side must only be connected to a PC.

Check if the micro/CPLD is 5V tolerant. If not then you have to limit the 5V Tx line (if there is one present between the 8051 and CPLD. The 3.3V Tx line can be connected directly to a 5V Rx input without any modifications. The 5V Tx line is a bit more tricky. Some CPLDs cannot take 5V on a input pin but will still be OK at 4.2V. For devices like these you can send the signal through a 160 ohm resistor and tie the output (after the resistor) with a 1n4148 diode to 3.3V (Anode on resistor, cathode on 3.3v). If this cannot be done then have a look at a voltage divider or switching an external transistor to pull down 3.3V at the input pin.


Victor

https://www.zerksus.com

 

[samuraign]

Hi All,
One side of my UART controller is on board RS232 traceiver,
will the other side of UART controller definetly needs a processor or DMA.
Can't I use the other side (lets say parallel 8bits)8bits to store directly into different
registers of my design in FPGA.These registers will be refreshed only at the
reset.

 

[cfriend]

If the volt level between CPLD and 8051 are compatible, you can connect the two devices together directly. Max232 is only a volt level converter chip to meet TIA/EIA-232 standard